Video display system, video display device, its control method, and information storage medium

ABSTRACT

To provide a video display system for allowing a user to look at and listen to video and sound on various means. A video display system has a video display device and a portable video display device, connected to each other for communication. The video display device produces own device video data and own device sound data to be displayed and reproduced, respectively, on the video display device; displays the own device video data and reproduces the own device sound data; encodes these data into a data format which the portable video display device is able to handle, to thereby produce other device video data and other device sound data; and sends to the portable video display device. The portable video display device receives these data, and decodes and displays the other device video data, and decodes and reproduces the other device sound data.

TECHNICAL FIELD

The present invention relates to a video display system, a video displaydevice, a control method for such as display device, and an informationstorage medium for displaying video and reproducing sound.

BACKGROUND ART

There is available a video display device for displaying video on amonitor of, e.g., a home-use television set receiver and the likeconnected thereto, and reproducing sound via a speaker of the same.Also, some of the video display devices are portable video displaydevices which can be carried by a user. As one example, these videodisplay devices read encoded video data and sound data from a computerreadable information storage medium, such as a DVD, a hard disk, and thelike, and then based on the read data, produces video data for display,in accordance with the capacity (size of the display screen and thelike) of a monitor, and sound data for reproduction, in accordance withthe capacity (the number of reproduction channels and the like) of aspeaker. Then, the produced video data is displayed on the monitor andthe produced sound data is reproduced via the speaker.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, according to the above-described conventional technique, thevideo display device merely outputs video data and sound data producedin accordance with its own monitor and speaker, or those connectedthereto, to these monitors and speakers. Therefore, a user can look atand listen to the video data and sound data read by the video displaydevice only on limited means.

The present invention has been conceived in view of the above, and oneof the objects of the present invention is to provide a video displaysystem, a video display device, a control method for the video displaydevice, and an information storage medium for making it possible for auser to look at and listen to video and sound on a variety of means.

Means to Solve the Problems

A video display system according to the present invention to attain theabove described objects is a video display system having a video displaydevice and a portable video display device, connected to each other forcommunication, wherein the video display device comprises own devicevideo data producing means for producing own device video data to bedisplayed on the video display device; own device sound data producingmeans for producing own device sound data to be reproduced on the videodisplay device; video and sound output means for displaying the producedown device video data and reproducing the produced own device sounddata; other device video data producing means for producing other devicevideo data in a data format different from a data format of the owndevice video data; other device sound data producing means for producingother device sound data in a data format different from a data format ofthe own device sound data; and data sending means for sending the otherdevice video data and the other device sound data to the portable videodisplay device, and the portable video display device comprises datareceiving means for receiving the sent other device video data and thesent other device sound data; and video and sound output means fordisplaying the received other device video data and reproducing thereceived other device sound data.

Also, another video display system according to the present invention isa video display system having a video display device and a portablevideo display device, connected to each other for communication, whereinthe video display device comprises own device video data producing meansfor producing own device video data to be displayed on the video displaydevice; own device sound data producing means for producing own devicesound data to be reproduced on the video display device; video and soundoutput means for displaying the produced own device video data andreproducing the produced own device sound data; encoding means forencoding the own device video data and the own device sound data into adata format which the portable video display device is able to handle,to thereby produce other device video data and other device sound data;and data sending means for sending the other device video data and theother device sound data to the portable video display device, and theportable video display device comprises data receiving means forreceiving the sent other device video data and the sent other devicesound data; and video and sound output means for decoding and displayingthe received other device video data and decoding and reproducing thereceived other device sound data.

Also, a video display device according to the present invention is avideo display device connected for communication to a portable videodisplay device, comprising own device video data producing means forproducing own device video data to be displayed on the video displaydevice; own device sound data producing means for producing own devicesound data to be reproduced on the video display device; video and soundoutput means for displaying the produced own device video data andreproducing the produced own device sound data; encoding means forencoding the own device video data and the own device sound data into adata format which the portable video display device is able to handle,to thereby produce other device video data and other device sound data;and data sending means for sending the other device video data and theother device sound data to the portable video display device.

In the above described video display device, the encoding means mayconvert the own device video data into a size which the portable videodisplay device is able to display, and then encode the own device videodata that has been converted in size, to thereby produce the otherdevice video data.

Also, in the above described video display device, the encoding meansmay reduce a number of channels of the own device sound data, and thenencode the own device sound data having a reduced number of channels, tothereby produce the other device sound data.

Also, in the above described video display device, the own device videodata producing means may decode encoded video data stored in storagemeans, to thereby produce the own device video data, the own devicesound data producing means may decode encoded sound data stored in thestorage means, to thereby produce the own device sound data, and theencoding means may encode at least one of the own device video data andthe own device sound data into a data format different from that of theencoded video data and the encoded sound data stored in the storagemeans.

Also, in the above described video display device, the encoding meansmay encode at least one of the own device video data and the own devicesound data into a data format selected based on information receivedfrom the portable video display device.

Also, the above described video display device may further comprisedisplay mode switching means for receiving a connection start requestand a connection end request sent from the portable video displaydevice, then switching a display mode to an other device display mode inresponse to the received connection start request and to an own devicedisplay mode in response to the received connection end request; whereinthe own device video data producing means may output the produced owndevice video data to a predetermined frame buffer when the display modeis the own device display mode, and to a memory area different from theframe buffer when the display mode is the other device display mode, theown device sound data producing means may output the produced own devicesound data to a predetermined sound buffer when the display mode is theown device display mode, and to a memory area different from the soundbuffer when the display mode is the other device display mode, the videoand sound output means may read and display the own device video datafrom the frame buffer, and may read and reproduce the own device sounddata from the sound buffer, and the encoding means may read and encodethe own device video data and the own device sound data from the memoryareas.

Also, the above described video display device may be connected forcommunication to a plurality of portable video display devices, and mayfurther comprise information holding means for holding informationcorrelating each of the portable video display devices to any of aplurality of groups, and the encoding means may produce a plurality ofsame or different other device video data and a plurality of same ordifferent other device sound data for the respective groups, and thedata sending means may send the other device video data and the otherdevice sound data produced for the respective groups to the respectiveportable video display devices correlated to the respective groupsaccording to the held information.

Also, a control method for a video display device according to thepresent invention is a control method for a video display deviceconnected for communication to a portable video display device,comprising a step of producing own device video data to be displayed onthe video display device; a step of producing own device sound data tobe reproduced on the video display device; a step of displaying theproduced own device video data and reproducing the produced own devicesound data; a step of encoding the own device video data and the owndevice sound data into a data format which the portable video displaydevice is able to handle, to thereby produce other device video data andother device sound data; and a step of sending the other device videodata and the other device sound data to the portable video displaydevice.

Also, an information storage medium according to the present inventionis a computer readable information storage medium storing a program forcausing a video display device connected for communication to a portablevideo display device to function as own device video data producingmeans for producing own device video data to be displayed on the videodisplay device; own device sound data producing means for producing owndevice sound data to be reproduced on the video display device; videoand sound output means for displaying the produced own device video dataon video display means and reproducing the produced own device sounddata on sound reproducing means; encoding means for encoding the owndevice video data and the own device sound data into a data format whichthe portable video display device is able to handle, to thereby produceother device video data and other device sound data; and data sendingmeans for sending the other device video data and the other device sounddata to the portable video display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a hardware structural diagram of an entertainment systemaccording to an embodiment of the present invention;

FIG. 2 is a detailed structural diagram of an MPU;

FIG. 3 is a hardware structural diagram of a portable video displaydevice according to the embodiment of the present invention;

FIG. 4 is a functional block diagram showing an example of a function ofa video display system according to an embodiment of the presentinvention;

FIG. 5 is a flowchart of an example of a process to be carried out bythe video display system according to the embodiment of the presentinvention;

FIG. 6 is a diagram for conceptually explaining an example of connectionbetween an entertainment system and a plurality of portable videodisplay devices; and

FIG. 7 is a diagram for explaining an example of a table held by theentertainment system according to the embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, one embodiment of the present invention will bedescribed with reference to the accompanying drawings. A video displaysystem according to this embodiment comprises an entertainment system 10operating as a video display device and a portable video display device50. The entertainment system 10 is connected to the portable videodisplay device 50 via a radio communication network for mutual dataexchange.

FIG. 1 is a diagram showing a hardware structure of an entertainmentsystem according to this embodiment. As shown in the diagram, theentertainment system 10 is a computer system comprising an MPU (MicroProcessing Unit) 11, a main memory 20, an image processing unit 24, amonitor 26, an input output processing unit 28, a sound processing unit30, a speaker 32, an optical disc reading unit 34, a hard disk 38,interfaces (I/F) 40, 44, a controller 42, a camera unit 46, and anetwork interface 48.

FIG. 2 is a diagram showing a structure of the MPU 11. As shown in thediagram, the MPU 11 comprises a main processor 12, sub-processors 14 a,14 b, 14 c, 14 d, 14 e, 14 f, 14 g, 14 h, a bus 16, a memory controller18, and an interface (I/F) 22.

The main processor 12 carries out various information processes andcontrols the sub-processors 14 a to 14 h, based on an operating systemstored in a ROM (Read Only Memory) (not shown), a program and data readfrom the optical disc 36, such as, e.g., a DVD (Digital VersatileDisk)-ROM and so forth, and a program and data supplied via acommunication network and so forth.

The sub-processors 14 a to 14 h carry out various information processesaccording to an instruction from the main processor 12, and control therespective units of the entertainment system 10, based on a program anddata read from the optical disc 36, such as, e.g., a DVD-ROM and soforth, and a program and data supplied via a communication network andso forth.

The bus 16 is used for exchanging an address and data among therespective units of the entertainment system 10. The main processor 12,sub-processors 14 a to 14 h, memory controller 18, and interface 22 areconnected to one another via the bus 16 for mutual data exchange.

The memory controller 18 accesses the main memory 20 according to aninstruction from the main processor 12 and sub-processors 14 a to 14 h.A program and data read from the optical disc 36 and/or hard disk 38 anda program and data supplied via a communication network are written intothe main memory 20 as required. The main memory 20 is used as a workingmemory of the main processor 12 and sub-processors 14 a to 14 h.

The image processing unit 24 and input output processing unit 28 areconnected to the interface 22, via which data exchange between the mainprocessor 12 and sub-processors 14 a to 14 h, and the image processingunit 24 or input output processing unit 28, is carried out.

The image processing unit 24 comprises a GPU (Graphical Processing Unit)and a frame buffer. The GPU renders various screen images into the framebuffer, based on image data supplied from the main processor 12 andsub-processor 14 a to 14 h. A screen image formed in the frame buffer isconverted into a video signal at a predetermined time and then output tothe monitor 26. Note that, e.g., a home-use television set receiver isused as the monitor 26.

The input output processing unit 28 is connected to the sound processingunit 30, optical disc reading unit 34, hard disk 38, interfaces 40, 44,and network interface 48. The input output processing unit 28 controlsdata exchange between the main processor 12 and sub-processors 14 a to14 h and the sound processing unit 30, optical disc reading unit 34,hard disk 38, interfaces 40, 44, and network interface 48.

The sound processing unit 30 comprises an SPU (Sound Processing Unit)and a sound buffer. Various sound data, such as game music, game soundeffects, messages, and so forth, read from the optical disc 36 and/orhard disk 38 are stored in the sound buffer. The SPU reproduces thevarious sound data and outputs via the speaker 32. Note that, e.g., aspeaker built into a home-use television set receiver is used as thespeaker 32.

The optical disc reading unit 34 reads a program and data recorded inthe optical disc 36 according to an instruction from the main processor12 and/or sub-processors 14 a to 14 h. Note that the entertainmentsystem 10 may be formed capable of reading a program and data stored ina computer readable information storage medium other than the opticaldisc 36.

The optical disc 36 is a general optical disc (a computer readableinformation storage medium), such as, e.g., a DVD-ROM or the like. Thehard disk 38 is a general hard disk device. Various programs and dataare stored in the optical disc 36 and/or hard disk 38 in a computerreadable manner.

The interfaces (I/F) 40, 44 are interfaces for connecting variousperipheral devices, such as the controller 42, camera unit 46, and soforth. A USB (Universal Serial Bus) interface, for example, may be usedas such an interface. Also, a radio communication interface, e.g., aBluetooth (registered trademark) interface and the like, may be used.

The controller 42 serves as a general purpose operation input means foruse by a user to input various operations (e.g., a game operation). Theinput output processing unit 28 scans the states of the respective unitsof the controller 42 every predetermined period of time (e.g., 1/60^(th)of a second), and supplies an operational signal describing the scanningresult to the main processor 12 and sub-processors 14 a to 14 h. Themain processor 12 and sub-processors 14 a to 14 h determine the contentof an operation carried out by a user, based on the operational signal.Note that the entertainment system 10 is formed capable of beingconnected to a plurality of controllers 42 so that the main processor 12and sub-processors 14 a to 14 h can carry out various processes based onthe operation signals input from the respective controllers 42.

The camera unit 46 comprises, e.g., a publicly known digital camera, andinputs a captured black and white, grayscale, or colored image everypredetermined period of time (e.g., 1/60^(th) of a second). The cameraunit 46 in this embodiment inputs a captured image as video data in JPEG(Joint Photographic Experts Group) format. The camera unit 46 is mountedon the monitor 26, having the lens thereof directed to, e.g., the user,and is connected via a cable to the interface 44. The network interface48 is connected to the input output processing unit 28 and acommunication network to relay data communication made by theentertainment system 10 via the communication network to anotherentertainment system 10.

Note that a radio communication interface, such as, e.g., a Bluetooth(registered trademark) interface, may be used as the network interface48. In this embodiment, the network interface 48 is connected to a radiocommunication network to relay data communication between theentertainment system 10 and portable video display device 50 via theradio communication network.

Meanwhile, the portable video display device 50 is a device, e.g., aportable game device or the like, for video display and soundreproduction, and can be carried by a user. In this embodiment, as shownin FIG. 3, the portable video display device 50 comprises an MPU 52, amain memory 54, an image processing unit 56, a monitor 58, an inputoutput processing unit 60, a sound processing unit 62, a speaker 64, anoptical disc reading unit 66, a controller 68, and a network interface70.

The MPU 52 carries out various information processes and controls therespective units of the portable video display device 50, based on anoperating system stored in a ROM (not shown) and a program and data readfrom an optical disc, such as, e.g., a UMD (registered trademark) or thelike, and a program and data supplied via a communication network.

The program and data read from an optical disc and a program and datasupplied via a communication network are written into the main memory 54when necessary. The main memory 54 is used as a working memory of theMPU 52.

The image processing unit 56 comprises a GPU and a frame buffer. The GPUrenders various screen images into a frame buffer, based on image datasupplied from the MPU 52. The screen image formed in the frame buffer isconverted into a video signal at a predetermined time, and then outputto the monitor 58. Note that the monitor 58 may be, e.g., a liquidcrystal display device formed integrally with the main body of theportable video display device 50.

The input output processing unit 60 is connected to the sound processingunit 62, optical disc reading unit 66, and network interface (I/F) 70.The input output processing unit 60 controls data exchange between theMPU 52 and the sound processing unit 62, optical disc reading unit 66,and network interface 70.

The sound processing unit 62 comprises an SPU and a sound buffer.Various sound data, such as game music, game sound effects, messages,and the like, read from an optical disc is stored in the sound buffer.The SPU reproduces these various sound data items and outputs via aspeaker 64. Note that the speaker 64 is built into the main body of theportable video display device 50.

The optical disc reading unit 66 reads a program and data stored in anoptical disc according to an instruction from the MPU 52. Note that theportable video display device 50 may be formed capable of reading aprogram and data stored in a computer readable information storagemedium other than an optical disc. Various programs and data are storedin the optical disc in a computer readable manner.

The controller 68 is a general purpose operation input means for use bya user to input various operations (e.g., game operation). Anoperational signal describing the content of an operation carried out bya user using the controller 68 is supplied by the input outputprocessing unit 60 to the MPU 52 every predetermined period of time.Note that the controller 68 has an operating member, such as variousbuttons and the like, equipped in the enclosure of the portable videodisplay device 50.

The network interface 70 is connected to the input output processingunit 60 and a radio communication network, and relays data communicationbetween the portable video display device 50 and entertainment system10.

In the following, a function realized by the video display systemcomprising the above described entertainment system 10 and portablevideo display device 50 will be described. In the embodiment, theentertainment system 10 produces video data for its own device (owndevice video data) to be displayed on the monitor 26 and sound data forits own device (own device sound data) to be reproduced via the speaker32. Then, video display and sound reproduction are carried out based onthese data items. Also, the entertainment system 10 produces video datafor another device (other device video data) which is in a differentdata format from that of the own device video data, and sound data foranother device (other device sound data) which is in a different dataformat from that of the own device sound data. The entertainment system10 has a function for sending these data items to the portable videodisplay device 50. The portable video display device 50 has a functionfor receiving these data items having been sent, and displays video onthe monitor 58 and reproduces sound via the speaker 64, based on thereceived data.

FIG. 4 is a functional block diagram showing one example of a functionrealized in the video display system according to this embodiment. Here,an example in which other device video data and other device sound dataare produced based on the own device video data and own device sounddata will be described.

As shown in FIG. 4, the entertainment system 10 functionally comprises adisplay mode switching unit 101, an own device video data producing unit102, an own device sound data producing unit 103, a video and soundoutput unit 104, an other device video data producing unit 105, an otherdevice sound data producing unit 106, and a data sending unit 107. Thesefunctions can be realized by the MPU 11 by executing a program stored inthe main memory 20. The program may be provided being stored in variouscomputer readable information storage media, such as, e.g., a CD-ROM, aDVD-ROM, a memory card, and the like, or alternatively via a network,such as the Internet or the like.

Also, as shown in FIG. 4, the portable video display device 50functionally comprises a mode switching control unit 108, a datareceiving unit 109, a received video data decoding unit 110, a receivedsound data decoding unit 111, and a video and sound output unit 112.These functions can be realized by the MPU 52 by executing a programstored in the main memory 54. This program maybe provided being storedin various computer readable information storage media, such as anoptical disc, a memory card, and the like, or alternatively via anetwork, such as the Internet, or the like.

Initially, respective functions realized by the entertainment system 10will be described.

The display mode switching unit 101 receives a connection start requestand a connection end request from the portable video display device 50,and switches the display mode in response to the received request.Specifically, the display mode switching unit 101 switches the displaymode to an other device display mode upon receipt of a connection startrequest and to an own device display mode upon receipt of a connectionend request. Note that the entertainment system 10 operates in the owndevice display mode until receipt of a connection start request from theportable video display device 50 in this embodiment.

The own device display mode is a mode in which the entertainment system10 outputs intact video data and sound data, produced for display andreproduction on its own device, to the monitor 26 and speaker 32,respectively, while the other device display mode is a mode in which theentertainment system 10 outputs the video data and sound data afterconverting into a data format which the portable video display device 50can handle and process, so that the portable video display device 50 cancarry out video display and sound reproduction. The respective units tobe described below operate differently depending on the modes.

The own device video data producing unit 102 produces video data(hereinafter referred to as own device video data) to be displayed onthe monitor 26 of the entertainment system 10.

As a specific example, the own device video data producing unit 102decodes the encoded video data stored in a storage means, such as theoptical disc 36, hard disk 38, and the like, to thereby produce owndevice video data. For example, the own device video data producing unit102 decodes the encoded video data stored in the optical disc 36 and thelike to thereby produce own device video data constituted by images tobe displayed on the monitor 26 every predetermined period of time (e.g.,every 1/60^(th) of a second). Note that the produced own device videodata is video data having a size in accordance with the size of an imagewhich can be displayed on the monitor 26.

Note that the own device video data produced by the own device videodata producing unit 102 is not limited to those obtained by decodingencoded video data. For example, the own device video data may be onefor a game screen image and/or a content selection menu screen imageproduced by executing a program stored in the optical disc 36 and thelike. Alternatively, the own device video data may be one produced basedon data obtained by the entertainment system 10 via a communicationnetwork and the like. Further, the own device video data may be videodata containing an image formed by placing an information presentationimage (an image presenting to a user various information items such as areproduction time and the like) and/or an operation target image (animage representing an icon, a menu item, and the like to be operated bya user) over a frame image showing content, such as movie and the like,obtained by decoding the encoded video data.

Here, the own device video data producing unit 102 switches thedestination to which to output the produced own device video data,depending on the display mode. Specifically, the own device video dataproducing unit 102 outputs the produced own device video data to a framebuffer in the image processing unit 24 when the display mode is the owndevice display mode, and to a memory area M1 that is different from theframe buffer in the main memory 20 when the display mode is the otherdevice display mode.

The own device sound data producing unit 103 produces sound data(hereinafter referred to as own device sound data) to be reproduced viathe speaker 32 of the entertainment system 10. As a specific example,the own device sound data producing unit 103 decodes the encoded sounddata stored in a storage means such as the optical disc 36, hard disk38, or the like, to thereby produce own device sound data.

Note that, similar to the own device video data producing unit 102, theown device sound data produced by the own device sound data producingunit 103 is not limited to data obtained by decoding the encoded sounddata, and may be data produced by executing a program stored in theoptical disc 36 or the like. Also, the own device sound data may be oneobtained by combining sound data indicating content, such as movie,music, and the like, obtained by decoding the encoded sound data and asound signal indicating operation sound to be reproduced in response tooperation by a user etc. and/or various sound effects.

Here, the own device sound data producing unit 103 switches thedestination to which to output the produced own device sound data,depending on the display mode. Specifically, the own device sound dataproducing unit 103 outputs the produced own device sound data to a soundbuffer in the sound processing unit 30 when the display mode is the owndevice display mode and to a memory area M2 different from the soundbuffer in the main memory 20 when the display mode is the other devicedisplay mode. The memory area M2 may be either an area different fromthe above described memory area M1, or an area ensured contiguously inthe memory area M1.

The video and sound output unit 104 displays the own device video dataproduced by the own device video data producing unit 102 and reproducesthe own device sound data produced by the own device sound dataproducing unit 103. Specifically, the video and sound output unit 104reads the own device video data having been output to the frame buffer,and sequentially displays on the screen of the monitor 26 everypredetermined period of time. Also, the own device sound data havingbeen output to the sound buffer is read and reproduced via the speaker32.

Using the above described respective functions, the entertainment system10 displays video and reproduces sound by itself, based on the videodata and sound data stored in the optical disc 36 and the like when thedisplay mode is the own device display mode. With the above, a user canlook at and listen to content, such as, e.g., a movie or the like,and/or play a game.

When the display mode switching unit 101 switches the display mode tothe other device display mode, the other device video data producingunit 105 encodes the own device video data produced by the own devicevideo data producing unit 102 into a data format which the portablevideo display device 50 can handle and process, to thereby produce otherdevice video data.

Specifically, the other device video data producing unit 105 reads aframe image of each of the frames constituting own device video datafrom the memory area M1 and encodes into a predetermined data format tothereby produce other device video data. For example, the other devicevideo data producing unit 105 produces, through encoding, video data ina data format based on the MPEG-4 (Moving Picture Experts Group phase 4)standard. Note that the other device video data producing unit 105 mayselect a data format into which data is to be encoded from among aplurality of predetermined data format candidates, based on theinformation sent from the portable video display device 50.

Here, prior to encoding, the other device video data producing unit 105may convert the own device video data into a size which the portablevideo display device 50 can handle and display, and then encode the owndevice video data subjected to size conversion to thereby produce otherdevice video data. In this case, the size which the portable videodisplay device 50 can handle and display may be determined based on theinformation stored beforehand in the entertainment system 10, orinformation sent from the portable video display device 50. With theabove, even when the image size which the entertainment system 10 canhandle and display on the monitor 26 differs from that which theportable video display device 50 can handle and display on the monitor58, the entertainment system 10 can produce other device video datawhich can be displayed on the portable video display device 50, usingthe own device video data. With the above, it is possible to convert theown device video data originally produced for display on the monitor 26into data in a format suitable for encoding.

Also, prior to encoding, the other device video data producing unit 105may carry out color conversion on own device video data. Specifically,e.g., the other device video data producing unit 105 converts colordesignated in the RGB color space and contained in the own device videodata into color in the YUV color space.

Also, the data format of the other device video data produced by theother device video data producing unit 105 may differ from that of theencoded video data stored in the optical disc 36 or the like and decodedby the own device video data producing unit 102. With the other devicevideo data sent to the portable video display device 50, to be describedlater, the portable video display device 50 can display video datastored in the optical disc 36 or the like in a data format which theportable video display device 50 originally cannot handle and display.

When the display mode switching unit 101 switches the display mode tothe other device display mode, the other device sound data producingunit 106 encodes the own device sound data produced by the own devicesound data producing unit 103 into a data format which the portablevideo display device 50 can handle and display, to thereby produce otherdevice sound data.

Specifically, the other device sound data producing unit 106 reads theown device sound data from the memory area M2 and then encodes into apredetermined data format to thereby produce other device sound data.For example, the other device sound data producing unit 106 produces,through encoding, codec sound data of the MPEG-2 Part7 or MPEG-4 Part3standard. Alternatively, codec sound data of ATRAC3 (Adaptive TransformAcoustic Coding 3) or the like may be produced. Note that similar to theother device video data producing unit 105, the other device sound dataproducing unit 106 may select a data format into which data is to beencoded from among a plurality of predetermined data format candidates,based on the information sent from the portable video display device 50.

Here, prior to encoding, the other device sound data producing unit 106reduces the number of channels of the own device sound data into thenumber which the portable video display device 50 can handle forreproduction, and encodes the own device sound data that has been toreduction in the number of channels to thereby produce other devicesound data. In this case, the number of channels which the portablevideo display device 50 can handle for reproduction may be determinedbased on the information stored beforehand in the entertainment system10 or information sent from the portable video display device 50. Withthe above, when the number of channels which the entertainment system 10can handle for reproduction via the speaker 32 differs from that whichthe portable video display device 50 can handle for reproduction via thespeaker 64, the entertainment system 10 can produce other device sounddata which the portable video display device 50 can handle forreproduction, using the own device sound data.

Note that in this case, the other device sound data producing unit 106,for example, deletes sound data for one or more channels from the owndevice sound data having a plurality of channels, to thereby reduce thenumber of channels. Alternatively, the number of channels can be reducedby mixing sound data for a plurality of channels contained in the owndevice sound data. For example, the other device sound data producingunit 106 converts own device sound data having a 5.1 or 7.1 channelsystem into other device sound data having two channels.

Also, similar to the other device video data, the data format of theother device sound data produced by the other device sound dataproducing unit 106 may differ from that of the encoded sound data storedin the optical disc 36 or the like and decoded by the own device sounddata producing unit 103. With the other device sound data sent to theportable video display device 50, to be described later, the portablevideo display device 50 can reproduce sound data stored in the opticaldisc 36 or the like in a data format which the portable video displaydevice 50 cannot originally handle for reproduction.

The data sending unit 107 sends the other device video data produced bythe other device video data producing unit 105 and the other devicesound data produced by the other device sound data producing unit 106 tothe portable video display device 50 having sent a connection startrequest. Note that the data sending unit 107 may encrypt the otherdevice video data and other device sound data before sending. Note thatan encryption key used for encryption may be one stored beforehand inthe entertainment system 10 or one produced, based on the informationsent from the portable video display device 50, according to apredetermined method.

Also, the data sending unit 107 may change the data transfer speed,depending on the amount of the other device video data and other devicesound data held in a transmission waiting state in the main memory 20.Also, in addition to, or in the place of, change of the data transferspeed by the data sending unit 107, the other device video dataproducing unit 105 may change the encoding bit rate for other devicevideo data to produce through encoding. That is, when the amount of theother device video data and other device sound data in a transmissionwaiting state increases, the encoding bit rate for the other devicevideo data is made lower, and when the amount of the data in thetransmission waiting state decreases, the encoding bit rate for theother device video data is made higher. Similarly, the other devicesound data producing unit 106 may change the encoding bit rate for otherdevice sound data to be produced, depending on the amount of data in thetransmission waiting state. With the above, it is possible to adjust theamount of the video data and sound data in the transmission waitingstate, depending on the state of the communication network, andtherefore to send the other device video data and other device sounddata to the portable video display device 50 without excessivelyoccupying the communication network band.

In the following, respective functions realized by the portable videodisplay device 50 will be described.

In response to an instruction operation issued by a user to thecontroller 68, the mode switching control unit 108 switches the displaymode of the portable video display device 50, and sends a connectionstart request and a connection end request to the entertainment system10. Specifically, in response to a connection start instruction by auser, the mode switching control unit 108 switches the display mode to areceived data display mode, and sends a connection start request to theentertainment system 10. Also, in response to a connection endinstruction by a user, the mode switching control unit 108 switches thedisplay mode to an own device display mode, and sends a connection endrequest to the entertainment system 10. Note that the received datadisplay mode refers to a mode in which video display and soundreproduction is carried out based on the video data and sound data sentfrom the entertainment system 10, while the own device display moderefers to a mode in which video display and sound reproduction iscarried out based on the video data and sound data produced by its owndevice, similar to the case with the entertainment system 10.

When the mode switching control unit 108 switches the display mode tothe received data display mode, the data receiving unit 109 receives theother device video data and other device sound data sent from the datasending unit 107 of the entertainment system 10 to which a connectionstart request has been sent. Note that when encrypted data is sent fromthe data sending unit 107, the data receiving unit 109 decrypts theencrypted data to restore data before encryption. The decryption keyused in this case may be one stored beforehand in the portable videodisplay device 50 or one produced based on information held in theportable video display device 50 according to a predetermined method.

It is assumed in this embodiment that the other device video data andother device sound data received by the data receiving unit 109 arestored in a memory area M3 ensured in the main memory 54. Note that thememory area M3 may be divided to separately store the video data andsound data, or may be a single area.

The received video data decoding unit 110 decodes the encoded otherdevice video data received by the data receiving unit 109. Specifically,the received video data decoding unit 110 reads the other device videodata stored in the memory area M3, then carries out a decoding process,and outputs the obtained video data to a memory area M4 (an outputbuffer area) ensured in the main memory 54.

The received sound data decoding unit 111 decodes the encoded otherdevice sound data received by the data receiving unit 109. Specifically,the received sound data decoding unit 111 reads the other device sounddata stored in the memory area M3, then carries out a decoding process,and outputs the obtained sound data to a memory area M5 (an outputbuffer area) ensured in the main memory 54.

The video and sound output unit 112 displays the video data obtainedthrough decoding by the received video data decoding unit 110 andreproduces the sound data obtained through decoding by the receivedsound data decoding unit 111. Specifically, the video and sound outputunit 112 reads the video data from the memory area M4 and outputs therespective frame images constituting the video data to a frame buffer inthe image processing unit 56, to sequentially display screen images onthe monitor 58. Also, the video and sound output unit 112 reads sounddata from the memory area M5 and outputs to a sound buffer in the soundprocessing unit 62 to reproduce sound via the speaker 64.

Note that it is assumed that the video and sound output unit 112 outputsthe video data and sound data obtained through decoding at apredetermined time to the frame buffer and sound buffer. Specifically,it is assumed that the video and sound output unit 112 outputs the videodata to the frame buffer and sound data to the sound buffer at a timewhich enables synchronized video display and sound reproduction.

Note that it is assumed that the received video data decoding unit 110and received sound data decoding unit 111 decode other device video dataand other device sound data, respectively, received every predeterminedprocess unit. Also, note that it is assumed that the memory areas M4 andM5 respectively have sufficient capacity to store video data and sounddata for a plurality of process units. With the above, even in a case inwhich at least one of the received video data decoding unit 110 andreceived sound data decoding unit 111 does not complete the decodingprocess within a predetermined period of time (so-called over-run), thevideo and sound output unit 112 can continue video display and soundreproduction as long as video data and sound data is held in the memoryareas M4 and M5, respectively. Further, in this case, the received videodata decoding unit 110 and received sound data decoding unit 111 maychange the method for decoding, depending on the amount of unprocessedvideo data and sound data stored in the memory areas M4 and M5.Specifically, in the case when, for example, the decoding process by thereceived video data decoding unit 110 is delayed and the amount ofunprocessed video data having been buffered in the memory area M4 isthus reduced, the received video data decoding unit 110 changes thedecoding method to one which accelerates decoding of video data in thefollowing process unit. With the above, the portable video displaydevice 50 can address delay in the decoding process, while continuouslycarrying out the video display and sound reproduction.

Using the above described respective functions, the portable videodisplay device 50 can attain video display and sound reproduction, basedon the video data and sound data read by the entertainment system 10from the optical disc 36 and the like, and/or data produced by the MPU11 when the display mode is the received data display mode. With theabove, a user can look at and listen to the video and sound on theportable video display device 50, the video and sound being distributedfrom the entertainment system 10 connected for communication to theportable video display device 50.

Note that when the entertainment system 10 is operating in the otherdevice display mode and a user looks at and listens to video and soundon the portable video display device 50, the entertainment system 10 maydisplay on the monitor 26 information indicating that video and sound isbeing distributed to the portable video display device 50.

Also, it is assumed that the portable video display device 50 in the owndevice display mode produces video data which can be displayed on themonitor 58 and sound data which can be reproduced via the speaker 64,based on the data read by the optical disc reading unit 66 from, e.g.,an optical disc, and displays video on the monitor 58 and reproducessound via the speaker 64. With the above, by switching the display modein response to an instruction from a user, the portable video displaydevice 50 can output both video and sound produced by its own device andvideo and sound distributed from the entertainment system 10.

In the following, one example of a flow of a process to be carried outby the video display system according to this embodiment will bedescribed based on the flowchart shown in FIG. 5. Note that it isassumed, in the example shown in the diagram, that the entertainmentsystem 10 and portable video display device 50 are both operating in theown device display mode when beginning the process.

In the example shown in FIG. 5, initially, the portable video displaydevice 50 receives a connection start instruction issued by a user tothe controller 68 (S1). In response to the instruction, the modeswitching control unit 108 sends a connection start request to theentertainment system 10 (S2), and switches the display mode of theportable video display device 50 to the received data display mode (S3).

Further, the portable video display device 50 produces a decryption key,based on the predetermined device ID of its own device (S4). Then, basedon the other device video data and other device sound data sent from theentertainment system 10, a received content output process for videodisplay and sound reproduction is carried out (S5). Specifically, thedata receiving unit 109 receives encrypted data sent from theentertainment system 10 and then restores the other device video dataand other device sound data before encryption, using the decryption keyproduced at S4. Further, the received video data decoding unit 110 andreceived sound data decoding unit 111 decode the encoded video data andencoded sound data, respectively, obtained by the data receiving unit109. The video and sound output unit 112 displays the video data on themonitor 58 and reproduces the sound data via the speaker 64. Thisreceived content output process is repeated until a user issues aconnection end instruction to the controller 68 (S6).

Meanwhile, the entertainment system 10, having received the connectionstart request sent at S2, carries out the following process. That is,initially, the display mode switching unit 101 switches the display modeto the other device display mode (S7). Further, the entertainment system10 produces an encryption key for data transmission, based on the deviceID of the portable video display device 50 (S8). It is assumed here thatthe device ID of the portable video display device 50 is sent from theportable video display device 50, together with the connection startrequest.

Subsequently, in response to a request from the portable video displaydevice 50, the entertainment system 10 carries out a contentdistribution process to produce other device video data and other devicesound data, and send the produced data to the portable video displaydevice 50 (S9). Specifically, the other device video data producing unit105 encodes the own device video data produced by the own device videodata producing unit 102 into other device video data, while the otherdevice sound data producing unit 106 encodes the own device sound dataproduced by the own device sound data producing unit 103 into otherdevice sound data. Then, the data sending unit 107 encrypts the otherdevice video data and other device sound data, using the encryption keyproduced at S8, and then sends to the portable video display device 50.This content distribution process is repeated until the portable videodisplay device 50 sends a connection end request (S10).

When a user issues a connection end instruction to the controller 68 ofthe portable video display device 50, the portable video display device50 sends a connection end request to the entertainment system 10 (S11),and switches its own display mode to the own device display mode (S12).The entertainment system 10, having received the connection end request,accordingly switches its own display mode to the own device display mode(S13). With the above, the entertainment system 10 and portable videodisplay device 50 thereafter independently display video data andreproduce sound data produced by themselves.

Note that the portable video display device 50 in this embodiment mayfurther have a function for sending, in the received data display mode,information (instruction operation information) describing the contentof an instruction operation, carried out by a user with the controller68, to the entertainment system 10. In this case, according to theinstruction operation by the user, described by the instructionoperation information received from the portable video display device50, the entertainment system 10 changes the content of the own devicevideo data and own device sound data. For example, while consideringthat the instruction operation by the user described by the receivedinstruction operation information is carried out by the controller 42connected to the entertainment system 10, the entertainment system 10produces own device video data and own device sound data in response tothe instruction operation. With the above, according to the videodisplay system according to this embodiment, a user can operate, forexample, a character shown on the screen of the monitor 58 by issuing aninstruction operation to the controller 68, and can then look at andlisten to the video and sound which resultantly changes. With the above,the user can not only look at and listen to content, such as a movie,outputting the video and sound in a one-sided manner, but also can enjoycontent, such as a game and the like, having an interactive nature.

Further, in this case, the size of the memory area M3 where the otherdevice video data and other device sound data received by the abovedescribed data receiving unit 109 is stored may be changed according tothe type of the content instructed by a user. When content, such as amovie or the like, for which contents do not change in response to aninstruction operation by a user, is distributed, even though the videodata to be displayed and sound data to be reproduced are held in thememory area M3 for a substantial period of time because of the memoryarea M3 has a large size, serious inconvenience is not likely to becaused. However, for a game or the like, for which contents will changein response to an instruction operation by a user, a time lag whichwould be caused due to the large size of the memory area M3 beforeoutputting the video data and sound data received by the portable videodisplay device 50 may deteriorate the real time nature, since thecontent of the instruction operation by the user is not instantlyreflected in the content. Therefore, in distribution of content of atype which will change in response to an instruction operation by auser, the memory area M3 is arranged to have a smaller size so thatoccurrence of the above described problem can be reduced. Note that theportable video display device 50 may change the size of a memory area,instead of the memory area M3, for storing the video data and sound datarestored through decoding by the received video data decoding unit 110and received sound data decoding unit 111, depending on the type ofcontent.

In the following, an example in which the entertainment system 10 isconnected to a plurality of portable video display devices 50 will bedescribed.

In this case, the entertainment system 10 may send common other devicevideo data and other device sound data to the plurality of portablevideo display devices 50 having sent connection start requests.Alternatively, the entertainment system 10 may send mutually differentother device video data and other device sound data.

In the case where mutually different other device video data and otherdevice sound data are sent, the entertainment system 10 receives, forexample, device identification information (device ID and the like)identifying a respective portable video display device 50, sent from theportable video display device 50 together with the connection startrequest. Then, the other device video data and other device sound dataare sent to the transmission destination identified by the receiveddevice identification information. With the above, mutually differentother device video data and other device sound data can be sent to therespective portable video display devices 50 having sent the connectionstart requests.

Also, it is assumed that the entertainment system 10 may holdinformation correlating each of the plurality of portable video displaydevices 50 to any of a plurality of groups, and may send mutuallydifferent or the same other device video data and other device sounddata produced for the respective groups to the respective portable videodisplay devices 50 correlated to the respective groups.

In this case, the portable video display device 50 having sent aconnection start request to the entertainment system 10 sendsinformation identifying the group to which its own device belongs, tothe entertainment system 10, based on an instruction operation by a useror the like. In response to the information, the entertainment system 10produces information correlating the portable video display device 50 tosuch a group.

FIG. 6 is a diagram conceptually explaining one example of connectionbetween the entertainment system 10 and a plurality of portable videodisplay devices 50 in this case. In the example shown in the diagram,the entertainment system 10 manages three groups, namely, groups G1, G2,and G3, and holds information correlating the portable video displaydevices 50 a and 50 b to the group G1, the portable video display device50 c to the group G2, and the portable video display device 50 d to thegroup G3. FIG. 7 is a diagram showing one example of a table showinginformation correlating a portable video display device 50 to such agroup.

In the example shown in FIG. 6, the entertainment system 10 producesmutually different own device video data and own device sound data forrespective groups, and then encodes the data to thereby produce mutuallydifferent other device video data and other device sound data. Then, theother device video data and other device sound data produced for therespective groups are sent to the respective portable video displaydevices 50 correlated to the respective groups. With the above, theportable video display devices 50 a and 50 b display the same video andreproduce the same sound. Meanwhile, the portable video display devices50 c and 50 d display video and reproduce sound different from those forthe other portable video display devices 50. Note that the entertainmentsystem 10 may produce and send the same other device video data andother device sound data with respect to different groups according to apredetermined condition.

Further, in response to an instruction operation by a user or the like,the portable video display device 50 may send to the entertainmentsystem 10 information for changing the group to which its own devicebelongs, while receiving video and sound. According to the information,the entertainment system 10 updates the information, as shown as anexample in FIG. 7, correlating the portable video display device 50 to agroup. With the above, the portable video display device 50, whilereceiving content from the entertainment system 10, can change thecontent to be received to one being distributed to another portablevideo display device 50.

Also, irrespective of the information sent from the portable videodisplay device 50, the entertainment system 10 may change the group towhich a respective portable video display device 50 is correlated, basedon another condition. For example, the entertainment system 10 changesthe group to which a respective portable video display device 50 iscorrelated, according to change in the situation of the communicationnetwork among the respective portable video display devices 50 and/orthe state of content being produced.

According to the above described example, the user can select contentwhich they wish to look at and listen to from among a plurality ofcontent items distributed from the entertainment system 10, and changethe content to receive while receiving content. Also, when a pluralityof groups correspond to, e.g., a plurality of scenes in one game, aplurality of users can simultaneously participate in one game on aplurality of portable video display devices 50, and moreover, byswitching the scenes, the respective users can enjoy the same video andsound with other users at one time, and video and sound for a scenededicated to themselves, different from those for another user, atanother time.

It should be noted that the embodiment of the present invention is notlimited to the above described embodiment. For example, theentertainment system 10 and portable video display device 50 may beconnected via various communication networks, such as the Internet andthe like, in addition to a radio communication network. Also, althoughthe video and sound output unit 104 of the entertainment system 10reproduces sound via the speaker 32 and the video and sound output unit112 of the portable video display device 50 reproduces sound via thespeaker 64 in the above description, sound may be reproduced via anear-phone or the like connected to the respective devices instead.

Also, although the own device video data producing unit 102 outputs theproduced own device video data to either the frame buffer or memory areaM1, depending on the display mode in the above described embodiment, theown device video data may be output to the frame buffer in eitherdisplay mode. In this case, in the other device display mode, the otherdevice video data producing unit 105 sequentially reads frame imagesforming own device video data once output to the frame buffer, and thencarries out an encoding process to produce other device video data. Notethat the other device video data producing unit 105 may convert theimage data read from the frame buffer into a size which the portablevideo display device 50 can handle and display before outputting toanother memory area ensured in the main memory 20, and then carries outan encode process, based on the image data output to the memory area, toproduce other device video data.

Also, similar to the case with the video data, the own device sound dataproducing unit 103 may always output the own device sound data to thesound buffer irrespective of the display mode. In this case, the otherdevice sound data producing unit 106 carries out an encoding process,based on the own device sound data read from the sound buffer, toproduce other device sound data.

Also, although the entertainment system 10 carries out a process in theabove described embodiment, while selectively switching between the owndevice display mode, in which video is displayed on the monitor 26 andsound is reproduced via the speaker 32, and the other device displaymode, in which video and sound are distributed to the portable videodevice 50, the entertainment system 10 may operate in a differentdisplay mode. For example, the entertainment system 10 may operate in adisplay mode in which common video and sound are displayed andreproduced simultaneously on its own device and the portable videodisplay device 50. Alternatively, the entertainment system 10 mayoperate in a display mode in which mutually different video and soundare displayed and reproduced simultaneously on its own device and theportable video display device 50. Further, in this case, the otherdevice video data and other device sound data to be sent to the portablevideo display device 50 is not limited to those produced by encoding theown device video data and own device sound data, and may be thoseproduced through the process same as that which is carried out by theown device video data producing unit 102 and/or own device sound dataproducing unit 103.

The invention claimed is:
 1. A video display system comprising a videodisplay device and a portable video display device, connected to eachother for communication, wherein the video display device comprises: owndevice video data producing means for producing own device video data tobe displayed on the video display device; own device sound dataproducing means for producing own device sound data to be reproduced onthe video display device; video and sound output means for displayingthe produced own device video data and reproducing the produced owndevice sound data; other device video data producing means for producingother device video data in a data format different from a data format ofthe own device video data; other device sound data producing means forproducing other device sound data in a data format different from a dataformat of the own device sound data; and data sending means for sendingthe other device video data and the other device sound data to theportable video display device, a storing area that temporally stores theother device video data and the other device sound data, wherein contentrealized by the other device video data and the other device sound datais changed by an instruction of the user, and the portable video displaydevice comprises: data receiving means for receiving the sent otherdevice video data and the sent other device sound data; a memory areathat receives and stores data acquired from said video display device,wherein the size of said memory area is reduced when the portable videodisplay device instructs the video display device to output video andsound related to a video game, and video and sound output means fordisplaying the other device video data temporally stored and reproducingthe received other device sound data.
 2. A video display systemcomprising a video display device and a portable video display device,connected to each other for communication, wherein the video displaydevice comprises: own device video data producing means for producingown device video data to be displayed on the video display device; owndevice sound data producing means for producing own device sound data tobe reproduced on the video display device; video and sound output meansfor displaying the produced own device video data and reproducing theproduced own device sound data; encoding means for encoding the owndevice video data and the own device sound data into a data format whichthe portable video display device is able to handle, to thereby produceother device video data and other device sound data; and data sendingmeans for sending the other device video data and the other device sounddata to the portable video display device, a storing area thattemporally stores the other device video data and the other device sounddata, wherein content realized by the other device video data and theother device sound data is changed by an instruction of the user, andthe portable video display device comprises: data receiving means forreceiving the sent other device video data and the sent other devicesound data; a memory area that receives and stores data acquired fromsaid video display device, wherein a storage capacity of said memoryarea is reduced when the portable video display device instructs thevideo display device to output video and sound related to a video game,and video and sound output means for decoding and displaying the otherdevice video data temporally stored and decoding and reproducing thereceived other device sound data.
 3. A video display device connectedfor communication to a portable video display device, comprising: owndevice video data producing means for producing own device video data tobe displayed on the video display device; own device sound dataproducing means for producing own device sound data to be reproduced onthe video display device; video and sound output means for displayingthe produced own device video data and reproducing the produced owndevice sound data; encoding means for encoding the own device video dataand the own device sound data into a data format which the portablevideo display device is able to handle, to thereby produce other devicevideo data and other device sound data; and data sending means forsending the other device video data and the other device sound data tothe portable video display device, a storing area that temporally storesthe other device video data and the other device sound data, whereincontent realized by the other device video data and the other devicesound data is changed by an instruction of the user, wherein the videoand sound output means displays the other device video data temporallystored and reproduces the other device sound data temporally stored, andwherein a smaller memory area is allocated to store data acquired fromsaid video display device when the portable video display deviceinstructs the video display device to output video and sound related toa video game, as compared to when non-video game related data isinstructed to be received.
 4. The video display device according toclaim 3, wherein the encoding means converts the own device video datainto a size which the portable video display device is able to display,and then encodes the own device video data that has been converted insize, to thereby produce the other device video data.
 5. The videodisplay device according to claim 3, wherein the encoding means reducesa number of channels of the own device sound data, and then encodes theown device sound data having a reduced number of channels, to therebyproduce the other device sound data.
 6. The video display deviceaccording to claim 3, wherein the own device video data producing meansdecodes encoded video data stored in storage means, to thereby producethe own device video data, the own device sound data producing meansdecodes encoded sound data stored in the storage means, to therebyproduce the own device sound data, and the encoding means encodes atleast one of the own device video data and the own device sound datainto a data format different from that of the encoded video data and theencoded sound data stored in the storage means.
 7. The video displaydevice according to claim 3, wherein the encoding means encodes at leastone of the own device video data and the own device sound data into adata format selected based on information received from the portablevideo display device.
 8. The video display device according to claim 3,further comprising: display mode switching means for receiving aconnection start request and a connection end request sent from theportable video display device, then switching a display mode to an otherdevice display mode in response to the received connection start requestand to an own device display mode in response to the received connectionend request; wherein the own device video data producing means outputsthe produced own device video data to a predetermined frame buffer whenthe display mode is the own device display mode, and to a memory areadifferent from the frame buffer when the display mode is the otherdevice display mode, the own device sound data producing means outputsthe produced own device sound data to a predetermined sound buffer whenthe display mode is the own device display mode, and to a memory areadifferent from the sound buffer when the display mode is the otherdevice display mode, the video and sound output means reads and displaysthe own device video data from the frame buffer, and reads andreproduces the own device sound data from the sound buffer, and theencoding means reads and encodes the own device video data and the owndevice sound data from the memory areas.
 9. The video display deviceaccording to claim 3, wherein the video display device is connected forcommunication to a plurality of portable video display devices, andfurther comprises information holding means for holding informationcorrelating each of the portable video display devices to any of aplurality of groups, the encoding means produces a plurality of same ordifferent other device video data and a plurality of same or differentother device sound data for the respective groups, and the data sendingmeans sends the other device video data and the other device sound dataproduced for the respective groups to the respective portable videodisplay devices correlated to the respective groups according to theheld information.
 10. A control method for a video display deviceconnected for communication to a portable video display device,comprising: a step of producing own device video data to be displayed onthe video display device; a step of producing own device sound data tobe reproduced on the video display device; a step of displaying theproduced own device video data and reproducing the produced own devicesound data; a step of encoding the own device video data and the owndevice sound data into a data format which the portable video displaydevice is able to handle, to thereby produce other device video data andother device sound data; and a step of sending the other device videodata and the other device sound data to the portable video displaydevice, temporally storing in a storing area the other device video dataand the other device sound data, wherein content realized by the otherdevice video data and the other device sound data is changed by aninstruction of the user, displaying the other device video datatemporally stored and reproducing the other device sound data temporallystored, and wherein the memory is read faster due to a small totalmemory area when the portable video display device instructs the videodisplay device to output video and sound related to a video game, ascompared to when non-video game related data is instructed to bereceived.
 11. A non-transitory computer readable information storagemedium storing a program for causing a video display device connectedfor communication to a portable video display device to function as: owndevice video data producing means for producing own device video data tobe displayed on the video display device; own device sound dataproducing means for producing own device sound data to be reproduced onthe video display device; video and sound output means for displayingthe produced own device video data on video display means andreproducing the produced own device sound data on sound reproducingmeans; encoding means for encoding the own device video data and the owndevice sound data into a data format which the portable video displaydevice is able to handle, to thereby produce other device video data andother device sound data; and data sending means for sending the otherdevice video data and the other device sound data to the portable videodisplay device, a storing area that temporally stores the other devicevideo data and the other device sound data, wherein content realized bythe other device video data and the other device sound data is changedby an instruction of the user, wherein the video and sound output meansdisplays the other device video data temporally stored and reproducesthe other device sound data temporally stored, and wherein an area forstoring sound and video data within the memory is reduced in size whenthe portable video display device instructs the video display device tooutput video and sound related to a video game.